How to Nail Your Analytics Interviews

Question Types: Estimation

Know Your Stats

Here are some basic stats that would be handy in the estimation interview.

  1. General Knowledge
    1. 315 million people in the States
    2. 2.5 people per household
    3. 70 year life expectancy
  2. Industry specific – Look up the market cap of your target industry
    1. Online ads: $300B digital advertising spent worldwide
    2. Ecommerce: $3.5T
    3. Healthcare: $5T
  3. Use the 80/20 rule: Identify the 20% area you should be spending energy on and deploy your resources on it.
    1. 80% of traffic is on 20% of the roads
    2. 80% of a company’s revenue is generated from 20% of customers
    3. 80% of the product experience comes from the 20% of the UI

Derive the Stats

Once you know the basic statistics, try to derive a few on your own:

  • of college new grads = 300 M people / 70 life expectancy = 4.28 M new grads each year
  • storage is #users * #photos per user * #size
  • ads cost = click through rate * cost per click

The 5-Step Estimation Formula

  • Step 1 Clarify the intention
    • Are you expecting an actual number or just thought process?
    • Do I get any additional background information?
  • Step 2 Start making a few assumptions and write the assumptions on one side of the whiteboard.
    • “I’m going to list some assumptions and do the calculations along the way.”
    • “I will first do a top-down analysis and double check it with a bottom-up one.”
  • Step 3 Do a top down analysis
  • Step 4 Do a bottom up analysis
    • Start from the smallest unit
    • Now is a good time to ask the interviewer: “If you approve, I’ll brainstorm solutions for this use case.”
  • Step 5 Usually the interviewer would ask you to do bottom up and top down. If there is any huge discrepancy, be prepared to explain why (go back to your assumptions!)

Practice Questions

  1. What’s the revenue of McDonald’s?
  2. How many queries per second does Gmail get?
  3. How many elevators do you need for a 50-story building?

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